Ammonoids Belonging to the Family Tornoceratidae from the Devonian of Janczyce in the Holy Cross Mountains, Poland
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Hydrodynamically controlled anagenetic evolution of Famennian goniatites from Poland MARIUSZ NIECHWEDOWICZ and JERZY TRAMMER Niechwedowicz, M. and Trammer, J. 2007. Hydrodynamically controlled anagenetic evolution of Famennian goniatites from Poland. Acta Palaeontologica Polonica 52 (1): 63–75. This paper reports on the evolution of ammonoids belonging to the family Tornoceratidae from the Devonian of Janczyce in the Holy Cross Mountains, Poland. Steady and gradual changes in conch morphology of the goniatite lin− eage Phoenixites frechi–Tornoceras subacutum–T. sublentiforme occurred in concert with water shallowing during the deposition of the Lower Famennian cephalopod limestone. Biometric analysis of ammonoid conch and facies analysis of the cephalopod limestones have been applied to assess the possible relationship between shell geometry and envi− ronmental changes. Results show that ratios of whorl width / diameter as well as whorl width / whorl height decreased, while distance from the venter to the greatest whorl width / diameter increased with time, thereby reducing hydrody− namic drag of the shells, probably in response to increasing water turbulence. The interpretation presented here is in agreement with similar cases from the literature. However, this kind of environmentally controlled evolution has hith− erto been recognized only in Jurassic and Cretaceous ammonoids. Conch morphology may be considered as an indica− tor of palaeobathymetry. Key words: Ammonoidea, hydrodynamics, evolution, environmental changes, Devonian, Poland. Mariusz Niechwedowicz [[email protected]], Muzeum Wydziału Geologii, Uniwersytet Warszawski, ul. Żwirki i Wigury 93, PL−02−089 Warszawa, Poland; Jerzy Trammer [[email protected]], Instytut Geologii Podstawowej, Wydział Geologii, Uniwersytet Warszawski, ul. Żwirki i Wigury 93, PL−02−089 Warszawa, Poland. Introdution The extraordinarily rich material from the lower Famen− nian cephalopod limestone from Janczyce (Holy Cross Ammonoids are one of the most prodigious groups of fossil Mountains, Poland) offers new insights into patterns and animals; they have long attracted students of evolution due to factors controlling ammonoid evolution in the Palaeozoic. their outstanding fossil record, extraordinary diversification, The assemblage from Janczyce is strongly dominated by wide distribution and rapid extinction. While their fossil re− tornoceratid goniatitids, a group with worldwide distribu− cord is well documented, patterns of ammonoid evolution tion. Its representatives are common in the Middle and Up− have yet to be fully explored. The most commonly postulated per Devonian rocks of Europe (Holy Cross Mountains, factor controlling ammonoid evolution is sea level−fluctu− Rhenish Slate Mountains, Harz, Montagne Noire, Pyre− ation (e.g., Bayer and McGhee 1984; House 1993; Korn nees, Cantabrian Mountains), North Africa (Morocco, Al− 1995; Klug 2002; Wani 2003), which may lead to paedo− geria), Asia (Ural, Timan), Australia (Canning Basin), and morphosis, as documented by Korn (1995) for the Late De− North America (e.g., House and Price 1985; Becker 1993; vonian ammonoids, as well as to other evolutionary changes Becker et al. 2000). in ammonoid shell morphology. Commonly, such patterns of Institutional abbreviation.—MWG, Museum of the Faculty ammonoid shell modification are observed in successions re− of Geology, Warsaw University, Warsaw, Poland. cording the regressive phases of transgressive−regressive cy− cles. Falls in relative sea−level and increases in water turbu− lence can trigger evolutionary changes manifested in gradual modifiactions in ammonoid shell geometry. This pheno− Geological setting menon has been well documented among Mesozoic ammo− noids (e.g., Bayer and McGhee 1984; Jacobs et al. 1994). The goniatitid assemblage described herein was collected However, it is poorly known in their Palaeozoic counter− from the Janczyce section (GPS position data: 50°46’1.20” N, parts. This paucity of data on evolutionary patterns among 21°13’58.80” E), in the eastern Holy Cross Mountains, Po− goniatitids is apparently caused by the scarcity of appropriate land (Fig. 1). The outcrop is situated in the eastern part of the sections for population studies of this group. Łagów Syncline in the Kielce Region. The goniatitids were Acta Palaeontol. Pol. 52 (1): 63–75, 2007 http://app.pan.pl/acta52/app52−063.pdf 64 ACTA PALAEONTOLOGICA POLONICA 52 (1), 2007 Fig. 1. Location of the Janczyce area (A) within the Holy Cross Mountains (B) and its position within Poland (C). The Janczyce outcrop is marked with an asterisk. Map of the Holy Cross Mountains modified after Mizerski (1995). Janczyce geological map after Narkiewicz and Olkowicz−Paprocka (1983). collected from a 1.2 metre thick cephalopod limestone, part The cephalopod limestone of the Janczyce section was of the over 200 metres thick Łagów Beds (Makowski 1991; found in 1918 by Jan Samsonowicz, who mapped this area Matyja and Narkiewicz 1995; see Fig. 2). This unit is a series geologically (Makowski 1991). On the basis of goniatitid of generally poorly fossiliferous (except for small brachio− material from this section, Makowski (1962, 1991) described pods, tentaculitids, and rare goniatitids), regulary bedded, sexual dimorphism. dark−grey laminated marly limestones (Narkiewicz and Ol− According to Makowski (1991), the Janczyce cephalopod kowicz−Paprocka 1983). limestone is lenticular. It splits into a number of layers which The Janczyce cephalopod limestone contains a rich cepha− differ in colour and faunal composition. Makowski (1991) lopod fauna (goniatitids, cyrto− and orthoconic nautiloids) to− recognized five beds within this limestone (Fig. 2). He also gether with rare brachiopods, gastropods, and bivalves. These noted the presence of two sedimentary discontinuity surfaces rocks are very similar in lithology and age to other cephalopod stained with oxidized iron minerals. These mark the bound− limestone intercalations known from Europe and other parts of aries between Beds 1–2 and 3–4. the world. They occur in the Upper Devonian of the Rhenish The age of the cephalopod limestone has been determined Slate Mountains and the Harz Mountains (Germany), the using conodonts. Wolska (1967) identified the Fammenian Montagne Noire (France), the Moravian Karst (Czech Repub− Palmatolepis crepida Zone. More detailed studies have fur− lic), the Carnic Alps (Austria, Italy), the Cantabrian Moun− ther constrained the age to Middle (Szulczewski 1992; Matyja tains (Spain), and in the Anti−Atlas chains of southern Mo− and Narkiewicz 1995) or Upper Palmatolepis crepida Zone rocco (Wendt and Aigner 1985). (according to Woroncowa−Marcinowska 2002). NIECHWEDOWICZ AND TRAMMER—ANAGENETIC EVOLUTION OF GONIATITES 65 Material and methods Bed 5 The material used in this study was collected from a temporary outcrop—a trench dug in a field of a local farmer. After the fieldwork was finished, the exposure was covered. It is be− lieved that the Janczyce site may be completely worked−out. During the fieldwork in 2001 and 2002 a few hundred tornoceratid goniatites were collected. The first rich ammo− noid material coming from this locality was collected by Bed 4 Henryk Makowski in the middle of the twentieth century. Makowski was interested in the problem of sexual dimor− phism in ammonites, so that he collected and described only sedimentary adult specimens. Moreover, he gave only the diameters of his discontinuity specimens and did not measure other parameters of the shell (see Makowski 1991). We also noticed the presence of juve− nile and adolescent specimens. Therefore, both collections Bed 3 were compared, but only the present authors’ collection was Palmatolepis crepida used in this study. The measurements were taken from all ontogenetic stages of the ammonoids found. Accordingly, the original variability spectrum of the “palaeopopulations” for each part of the log was reproduced as accurately as pos− Bed 2 sible. FAMENNIAN sedimentary Ammonoid specimens, especially large ones, are usually 1m incompletely preserved. The body chamber is usually dam− Middle / Upper Zone discontinuity aged, and fragments of the aperture are preserved only in a few specimens. However, most of the goniatitids extracted 0 from the rocks are three−dimensionally preserved, which al− Bed 1 lowed us to use them in this study. The body chambers are marly limestones usually filled with silty sediment while the phragmocones shales 10 cm consist of clear calcite or are filled with silty sediment, which cephalopod limestones caused damage of the septa. Therefore in most specimens the early whorls cannot be observed. Ammonoids with incom− Fig. 2. Position of the studied Janczyce cephalopod limestones within the plete conchs, usually caused by body chamber damage, spec− complex of laminated marly limestones (Łagów Beds). Cephalopod lime− imen corrosion or erosion, were not used in this work. Many stone log after Makowski (1991). specimens have the wrinkle−layer structure preserved (see Niechwedowicz 2003) which is interpreted as “fingerprint”− junior synonym of T. typum by Korn and Klug (2002). How− like impression of the soft body (e.g., Senior 1971; Dogu− ever, differences in conch morphology and suture line be− zhaeva and Mutvei 1996). tween these forms allow us to regard Tornoceras sublenti− forme as a valid taxon. Becker (1993) suggested possible relationships between Description of goniatitid some representatives of the studied Tornoceratidae lineage and other Late Devonian species.